1. Field of the Invention
The present invention pertains to the field of producing fragment-free access openings, more particularly to the field of using explosive material to produce fragment-free openings in hardened structures such as doors or metal containers and most particularly to the field of using explosive material to produce fragment-free openings in hardened containers that house improvised explosive devices without initiating said devices.
2. Description of the Related Art
Bomb squad technicians regularly deal with packages that are suspected of containing explosive devices. In order to reduce the risks associated with opening such packages, technicians primarily use either robotic tools or explosive access tools that can be initiated from a distance. For certain types of packages or containers, robotic access tools, which often lack precision, power, and are cumbersome, cannot be employed. For these types of packages, such as metal drums or other hardened containers, explosive access tools are the only option.
Various explosive tools have been employed for this purpose. One technique is to employ a linear-shaped charge to create an opening in the hardened container. These shaped charges comprise a chevron-shaped metallic casing, which is usually copper, aluminum, or lead, that contains a quantity of high explosive. The charge cuts the hardened container by accelerating each side of the chevron-shaped wedge into each other, forming a high-velocity metallic jet. However, this technique, like merely using high explosives to directly cut into hardened targets, produces many fragments, which are capable of accidentally initiating any improvised explosive device within the container.
In order to alleviate this fragmentation problem, a device commonly known as the Magic Cube™ was developed and disclosed in U.S. Pat. No. 6,220,166. This device comprises a sheet explosive that is initiated at four different points and a buffer material, made up of three sheets of stacked, low density material, such as polyethylene foam which is placed between the explosive and the target. Various types of tapes and adhesives are required in order to combine these elements and affix the final device to the target. While the device does alleviate the fragmentation problem discussed above under certain circumstances, it does have several problems associated with its intended use. First, due to the complexity of the device, any particular embodiment is designed to operate on only one range of specific “wall” thickness. Second, also due to the complexity of the device, it is relatively expensive. Third, the device only operates effectively against flat surfaces. Finally, the device only works against hardened materials, such as steel, but does not work against softer metals such as aluminum.
Therefore, it is desired to provide an explosive access tool that produces no fragments, is inexpensive, and can be used on containers, made of varying materials, having various shapes and of varying wall thickness.